1. Field of the Invention
The invention relates to a hybrid vehicle, a controller for a hybrid vehicle, and a control method for a hybrid vehicle and, more particularly, to catalyst warm-up control in a hybrid vehicle that is provided with an internal combustion engine which includes a variable valve actuating device for changing an operation characteristic of an intake valve.
2. Description of Related Art
An exhaust emission control device including a catalyst is used so as to control an exhaust emission of an internal combustion engine. The temperature of the catalyst should be raised in order for the catalyst to fulfill a sufficient purification function.
As an example, Japanese Patent Application Publication No. 2012-40915 (JP 2012-40915 A) discloses a hybrid vehicle in which catalyst warm-up control for performing warm-up on the catalyst of the exhaust emission control device is executed. When the catalyst warm-up is required in this hybrid vehicle, the internal combustion engine is operated at a first operating point at which ignition timing of the internal combustion engine is on a retard side, and then the internal combustion engine is operated at a second operating point, at which an output demand for the internal combustion engine is fixed, with the ignition timing returned after the temperature in a catalyst end portion is raised. After the catalyst warm-up is completed, the process proceeds to a normal operation for changing the output demand for the internal combustion engine based on an output demand for the entire vehicle (refer to JP 2012-40915 A).
In addition, internal combustion engines that have variable valve actuating devices which are capable of changing operation characteristics of intake valves have been known. As such variable valve actuating devices, variable valve actuating devices that are capable of changing at least one of a valve lift and a valve operating angle of the intake valve have been known (refer to Japanese Patent Application Publication No. 2009-108720, Japanese Patent Application Publication No. 2004-183610, Japanese Patent Application Publication No. 2013-53610, Japanese Patent Application Publication No. 2008-25550, Japanese Patent Application Publication No. 2012-117376, Japanese Patent Application Publication No. 9-242519, and the like).